U.S. investigators are looking into why a SkyWest airplane with 75 passengers was forced to make an emergency landing in Buffalo on Wednesday.

The regional jet, which was headed from Chicago to Hartford, Conn., landed safely at Buffalo Niagara International Airport shortly before noon Wednesday after a passenger lost consciousness, a SkyWest official told The News.

“The flight landed safely in Buffalo, where the passenger received medical attention before being released. We are working to accommodate the 75 passengers to Hartford,” an official said.

The Federal Aviation Administration said in a statement that the flight crew reported a pressurization problem and declared an emergency before landing safely.

SkyWest also said there was no indication of any problems with the doors of the plane. Its mechanics conducted an inspection of the plane.

The regional jet, operating as United Express Flight 5622 under SkyWest, had 75 passengers and four crew members aboard when the problem occurred, according to Niagara Frontier Transportation Authority and SkyWest officials.

“I know that everyone has been checked out and cleared by EMTs, and nobody has been transported to the hospital,” SkyWest spokesman Layne Watson said.

The airline sent a replacement plane to Buffalo Wednesday afternoon, the passengers were going through the regular reboarding process and they were expected to leave “as soon as possible” to continue their trip to Hartford, according to C. Douglas Hartmayer, director of public affairs for the NFTA, operator of the airport.

Hartmayer said there were no injuries, and mechanics did not immediately find any defects in the grounded airplane.